Past studies have generally failed to detect any harmful effects from in utero exposure to Ultrasound in humans. Similar results have also been found in animal studies, although some evidence exists which suggests possible long-term abnormalities. Because of the previously known sensitivity of embryonic tissues to various insults (e.g., diagnostic radiation), it is important to thoroughly investigate the presently unknown long-term bioeffects of Ultrasound monitoring at various times during pregnancy. After intensive examination across several generations of animals should provide valuable information concerning any possible late- arising genetic abnormalities, and these result should be available well in advance of comparable information from human studies. Objectives of the studies described in this proposal are to evaluate effects of in-utero exposure to diagnostic Ultrasound in mice on reproductive systems and other organs across three generations of mice offspring. Studies will include evaluations of fertility in male and female offspring, lactate dehydrogenase-x (LDH-X) enzyme studies in male offspring, and gross anatomical and histological examination of male and female reproductive organs in offspring from all original "families". In addition, anatomical and histological examinations of other organs and tissues will be made from a specially selected sample of offspring. The Ultrasound exposure will include both pulsed and continuous waves at each of two intensity levels during each of two stages of pregnancy in mice. Male offspring will be mated with females of known fertility and female offspring will be mated with males of known fertility. Enzymes studies (LDH-X) will be performed on male offspring in each generation from each original family, and testes and ovaries will be examined anatomically and histologically from these same males and a similar sample of females, respectively. In addition, other reproductive organs (epididymus, prostate, uterus) and non-reproductive organs and tissues (thymus, bone marrow, spleen, brain and liver) will be examined in animals that show reproductive failure and in a randomly selected 10% of those that were included in the reproductive studies.